Lifi

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LIFI BASED DATA TRANSFER
Jahanavi Koppaka, ECE, Chilkur Balaji Institute of Technology, jahanavikoppaka@gmail.com.
B.Raghuveer, ECE, Chilkur Balaji Institute of Technology, raghurokz.ravi@gmail.com.
K.Aditya, ECE, Chilkur Balaji Institute of Technology, adityak0010@gmail.com.
ABSTRACT – These days the audio and video featured information transmission between two smart mobile devices requires some serious
energy and time. This paper gives the design of full-duplex wireless light correspondence framework, in view of Light fidelity (Li-Fi) which has
the capacity to transmit information bidirectionally all the while by utilizing Light-emitting diodes as a transmitter and Silicon Photodiodes as
recipient between two smartphone devices. This framework adds to a model to show a bidirectional remote correlation framework while taking
android devices into account. In this framework, two android mobiles telephones can transmit nearby information put away in the memory of
versatile to one another anybody portable either goes about as a transmitter or recipient. The framework comprises of two sections, for the most
part, one is equipment and another programming. The equipment configuration is taking into account the USB port coordinated to Android
Mobile. USB coordinated hardware gives USB to non-concurrent serial information exchange interface. The improvement of programming uses
the convention of Android Open Accessory which is another element in Android 3.1 or more propelled form by uniting outside span of USB
which permitting information transmission between Android gadgets over USB interfaces. Brushing with a USB port on one board, it can
accomplish up to 3Mbps bit rates slip free, which is mostly constrained to the USB extension circuit between two devices for information
transmission, for example, content, sound, and feature. The product is utilized to situate the transmission information rate, control bits and
check bits in order to accomplish ongoing and directional transmission between two devices with a USB port.
KEYWORDS – Photodiode, LED, USB, Data Transfer, Interface, Wireless, Android.
1 INTRODUCTION
The customary remote correspondence advancements
between cellular telephones are Bluetooth and IrDA Wi-Fi
too. They can't give a directional remote channel to two
telephones. This paper endeavors to fabricate another
transport by which the portable terminals can exchange
nearby information to one another at the same time. For
information transmission, we utilized Li-Fi innovation. Li-
Fi is the transmission of information through enlightenment
by taking the fiber out of fiber optics by sending information
through a LED light that differs in force quicker than the
human eye can follow. Li-Fi is the term some have used to
name the quick and shabby remote correspondence
framework, which is the optical adaptation of Wi-Fi.
The term was initially utilized as a part of this
setting by Harald Haas in his TED Global chat on Visible
Light Communication. "At the heart of this innovation is
another era of high brilliance light-discharging diodes", says
Harald Haas from the University of Edinburgh, UK,
"essentially, if the LED is on, you transmit a computerized
1, on the off chance that it's off you transmit a 0,"Haas says,
"They can be exchanged on and off rapidly, which gives
pleasant open doors for transmitted information." In
straightforward terms, Li-Fi can be considered as a light-
based Wi-Fi. That is, it uses light rather than radio waves to
transmit data.
Furthermore, rather than Wi-Fi modems, Li-Fi
would utilize handset fitted LED lights that can light a room
and in addition transmit and get data. Since straightforward
lights are utilized, there can actually be any number of
access focuses. This innovation utilizes a piece of the
electromagnetic range that is still not significantly used The
Visible Spectrum. Light is truth be told all that much piece
of our lives for millions and a large number of years and
does not have any significant sick impact. All the more over
yonder is 10,000 times more space accessible in this range
and simply depending on the globules being used, it
likewise duplicates to 10,000 times more accessibility as a
base, all inclusive.
It is conceivable to encode information in the light by
fluctuating the rate at which the LEDs glint on and off to
give diverse series of 1s and 0s. The LED force is tweaked
so quickly that human eyes can't see, so the yield seems
steady. More modern systems could significantly build VLC
information rates. Groups at the University of Oxford and
the University of Edinburgh are concentrating on parallel
information transmission utilizing varieties of LEDs, where
each LED transmits an alternate information stream.
Different gatherings are utilizing blends of red, green and
blue LEDs to modify the light's recurrence, with every
recurrence encoding an alternate information channel.
It has the ability to Tx information at a rate of 100
MB/s – which Is by and large speedier than most customary
UK broadband. In this paper, another transport by which the
portable terminal can exchange information to one another
is composed as a fundamental utilization of obvious light
correspondence on versatile terminals. Specially created
Software was utilized to Transmit and Receive the surge of
information between two Android gadgets.
2 DESIGN AND DEVELOPMENT
The module developed can work as USB host or slave.
The module can only operate in one mode at a time and
when it has no connected device, this will begin in host
mode. If a host-type device is connected to the module, the

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module switches to USB slave mode. The USB module in
this system is responsible for processing data sent from the
mobile device. The module acts as a USB host if connected
to a mobile.
Once the USB connection is established, the acquired
data is sent to the mobile device where they can be
Processed locally. The mobile devices will run a software
application which is designed to manage to send the local
data to a controller of USB i.e. FT230XB which is the
bridge circuit between the US B and LED or Photodiode
with mobile. The model of this system is shown in Fig.1.
Fig. 1: Model of System
In this system, the master chip of the external
module FT230XB connector circuit as shown in Fig.2,
which is responsible for the control and management of the
entire system, it has an internal USB protocol engine that
manages the data stream from the device USB control
endpoint
A. Full Speed USB to Basic UART – FT230X:
This USB2.0 Full Speed IC offers a compact bridge
to basic UART interfaces. The device is a UART, capable of
operating up to 3MBaud, with low power consumption
(8mA). The FT230X includes the complete FT-X series
feature set and enables USB to be added into a system
design quickly and easily over a UART interface. Fig 3
Shows Wire Connections of FT230XB
Highlights:
• Single chip USB to non-concurring serial
information exchange interface.
• Entire USB convention took care of on the chip.
No USB particular firmware programming needed.
• Fully incorporated 2048 byte EEPROM for putting
away gadget descriptors and CBUS I/O design.
• Fully incorporated clock era with no outer gem
needed in addition to discretionary clock yield
choice empowering a paste less interface to outside
MCU or FPGA.
• Data exchange rates from 300 baud to 3 M baud.
• 512 byte get Buffer and 512 bytes transmit support
using cradle smoothing innovation to take into
consideration high information throughput.
• FTDI's sans sovereignty Virtual Com Port (VCP)
and Direct (D2XX) drivers take out the necessity
for USB driver advancement much of the time.
• Configurable CBUS I/O pins.
• Transmit and get LED drive signals.
• UART interface support for 7 or 8 information bits,
1 or 2 stop bits and odd/even/mark/space/no
equality.
• Synchronous and non-concurring bit blast interface
alternatives with RD# and WR# strobes.
• Battery Charger Detection. May be utilized by cell
phones to identify the vicinity of a charger on the
USB port to empower higher current/quicker
charging of batteries.
• Device supplied pre-modified with extraordinary
USB serial number.
• Supports transport fueled, self-controlled and high-
power transport controlled USB setups.
• Integrated +3.3V level converter for USB I/O.
• True 3.3V CMOS drive yield and TTL
input.(operates down to 1V8 with outer force ups
and is additionally 5V tolerant)
• Configurable I/O pin yield drive quality.
• Integrated force on-reset circuit.
• UART signal reversal alternative.
• Internal 3.3V/1.8V LDO controllers
• Low working current of 8mA (run of the mill) and
USB suspend current of 125uA (common) current.
• Low USB data transfer capacity utilization.
• UHCI/OHCI/EHCI host controller good.
• USB 2.0 Full Speed perfect.
Fig.2: FT230XB Circuit Schematic
Fig.3: FT230XB Wire Connections

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B. Si PIN photodiode
The photodetector used for optical to electrical
Conversion with 150 mm2 effective active area, 14mm
active area size and 35° half angle. Fig. 4 shows directivity
curve for Si-PIN (Hamamatsu S6968) photodiode.
Highlights:
• Plastic packages with ɸ14mm lens
• High-speed4response:50MHz
• Type (VR=10V,λ=850nm)
• High sensitivity: 0.63A/W (l=850nm)
• Directivity: 35˚ (half angle)
• Active area size: ɸ 14mm (lens diameter)
• Effective active area: 150 mm2
Directivity:
Fig. 4: Directivity curve
C. Light Emitting Diode
A high power white Light Emitting Diode of
300mW and with the beam angle 120° is used as the
optical transmission source.
3 BLOCK DIAGRAM
Fig.5: Transceiver block diagram.
The implementation of an overall block diagram of
transceiver circuitry as shown in Fig.7 which gives signal
flow for data communication take place between two
android mobiles.
The application used for this system is designed with
the Eclipse Development Environment and Android and
Java Development Environment Fig.8 gives android
development configuration required for the designing oh
android application.
Fig. 6: Android Development Configuration
The development of the application utilizes the
protocol of AOA (Android Open Accessory) which is a new
feature whereby a USB host device can connect to the
Android device to allow data transfer to and from the
Android device over USB. Android supports USB host and
accessory modes directly from the version of Android 3.1.
USB accessory mode is also backported to Android 2.3.4 as
an add-on library to support a broader range of devices.
Device manufacturers can choose whether or not to include
the add-on library on the device's system image. The support
of these modes of operation depends on the hardware of the
device regardless of the platform level and it is structured in
Fig.7.
Fig.7 Functionality of the firmware for the Android USB
accessory mode.
The receiver employs a commercially available
photodetector Si PIN photodiode receives optical signal
which is sent to a low-pass filter followed by a custom
amplifier for recovery then decision circuit (LT1715)
issued as a single threshold voltage comparator to achieve
the signal decision with a reference voltage level to obtain
the original signal after that FT230XB achieve the
conversion from TTL signal to USB serial signal. Fig.5
shows the implementation of receiver circuit diagram.
Similarly, at the transmitter side, FT230 will realize the
conversion of the signal of USB from differential to TTL.
Then a voltage follower connected to the output pin of
FT230 pull up the signal current to an adequate level,
driving LED for lighting. A high power white light LED of
300mW and with the beam angle, 120° is used as the
optical transmission source. OOK NRZ data for Intensity
modulation (IM) and direct detection (DD) scheme is
chosen for the wide reception in VLC research. Fig.6
shows the implementation of transmitter circuit diagram.
The microcontroller firmware functionality will be
confirmed as shown in Fig.9, to establish a data connection

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between mobile devices that support USB accessory. The
software application was developed using the example
provided by FTDI Company. As it was stated before, the
Eclipse Development Environment with the Android SDK
and platform 3.1 or more advanced are used.
When the developed application is installed in the
mobile phone, the software will detect the USB port once a
module is plugged in, then it will read the Product ID and
vector ID stored in the EEPROM as shown in Fig.8 of the
FT230XB integrated in the module to determine whether
the connector is enumerated and supported by the software
through looking up the enumerated list integrated in the
software in advance.
The application can transfer the local data chosen by
the operator to the bit streams and send it to the USB port,
such as text, audio, video and so on as shown in Fig.9 and
Fig.10. The external module will transfer the signal from
the USB and drive the LED. After a Line of sight channel,
the opposite transceiver module plugged into the USB port
of the second mobile receives the bit streams and recovers
the bit streams to the original data. The developed
application for data transmission also support to other
types of FTDI D2xx family chip and according to device
interfaced to mobile, we set baud rate, data bit, parity, and
flow. The application can transfer any type of file through
the connected FT230XB connector to an android device.
Fig. 8: Software screenshot which read Product ID and
Vector ID of FT2030XB
Fig. 9: Software Screenshot of UART data transmission
• This application displays the functionality of
UART.
• The first row contains an Open button to open
selected Port numbers and a Config to set UART
configuration with several selectable setting items.
• The UART configuration settings allow the baud
rate to be set at standard values between 300 and
921600 baud.
• Stop bits may be set for 1 or 2.
• Data bits may be set for 7 or 8.
• Parity may be set for ODD, EVEN, Mark, Space,
None.
• The Read Bytes box displays the received data as
ASCII values.
• The Read Enabled button is used to test stop/restart
in task APIs.
• Read Enabled will switch to read Disabled when
tapped, causing the application to stop receiving
data.
• Tap it again to enable the receive functionality.
• Write Bytes allows a user to type in plain text and
send it by tapping Write.
This application receives and sends data from and to
Android device itself if an ‘FT230XB’ module is connected
to the mobile device.
4 RESULTS
With this system, the ultimate performance of USB
module can be measured. In the LED communication
system, the optical power of the LED would be stronger
and less susceptible to distance as the distance between
the transmitter and receiver circuit goes on increasing. As
input-output waveform shown in fig.6.
Fig.6: Input-output waveform of wireless
communication system
By using this technology 3Mbps speed can be
achieved using the wireless LED diode communication
with the transmitter input as the green signal and the
receiver output as the green signal. We can find there is
an existence of time delay in this system. By comparing
the signal waveform, It is clearly that there is little error

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bit after visible light transmission through the system.
Although the signal that the receiver output is not the
standard rectangular wave, the decision algorithm inside
the controller board is able to detect errors in the data and
provide a correct error free output pattern.
5 CONCLUSION
In this paper, we developed a Half Duplex optical
wireless system prototype to achieve the transmission
between two android mobiles using the LED. The
integration of an electronic device with the hardware and
software of mobile devices for personal use was presented.
This device is able to take advantage of the main features of
mobile devices, allowing users to transmit the local data to
each other like Bluetooth Wi-Fi. The upper limit
transmission rate is 3 Mbit/s .The transmission bandwidth of
the LED is very high. The proposed system uses the USB
2.0 so the speed is limited to the USB protocol version and
high-speed communication can be achieved by using higher
level protocol version of the USB.
ACKNOWLEDGMENT
We are very thankful to The Department of Electronics
and Communication Engineering of (CBIT) Chilkur Balaji
Institute of Technology, Affiliated to JNTU Hyderabad for
providing the required facilities and guidance needed for the
successful completion of this paper.
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Communications using Blind Equalization,” Processing of
Communications and Photonics Conference, 13-16 November 2011,
[3] VLCC, “Visible Light Communications Consortium,” 2008. [4] M.
Nakagawa, “Visible Light Communications,” 2007. Komine T,
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